A leash holder for the seemingly standard size rolls of dog poop bags.
Uploaded stls will fit rolls ~60mm tall with a ~30mm diameter, and a ~1.5mmx27mm leash.
The included FreeCAD file is reasonably customizable by editing values in the Parameters spreadsheet. If you use a different size nozzle than 0.4mm, changing the line width variable will ensure wall thicknesses are a multiple of your nozzle width.
Freecad file and STLs can also be found on github.